A magnetic recording head generally includes two portions: a writer portion for storing encoded information on a magnetic recording medium, such as a disk or tape, and a reader portion for retrieving recorded information from the medium. In the case of perpendicular recording, the writer portion typically includes a single writing pole and one or more return poles. The standard configuration has a single return pole situated upstream of the write pole.
The poles are made of magnetic material and are separated from each other at the recording surface by a non-magnetic, or poorly magnetic, gap layer. Current flowing through conductive coils is generally used to create magnetic flux that is carried through the writing pole. This creates a magnetic field at the magnetic medium, setting its magnetization and encoding information for later retrieval by the reader. The flux returns to the writer through one or more return poles.
Diagrams showing the configuration of a magnetic recording write head in a disk drive and a tape drive are shown, respectively, in FIGS. 1a and 1b. The axes labeled X, Y, Z depict the relative directions of downstream, across-track, and above-head surface.
The magnetic field emanating from the write head into the medium is distributed at various angles relative to the medium surface. The medium easy axis (or anisotropy) direction is the direction of lower energy and therefore preferred direction of magnetization. The easy axis is designed to be uniform and typically in the direction perpendicular to the medium surface for perpendicular recording (or vertical recording).
Directions perpendicular to the easy axis are typically considered the hard axis direction. The write field at the medium produced by the write head is in the easy axis direction for some portions of the write field and may contain hard axis components in other portions of the write field. Hard axis fields during writing are an issue in perpendicular recording.